Power-refrigeration system



.July 13, 1965 J. K. LA FLEUR POWER-REFRIGERATION SYSTEM Filed 001;. 24,1963 m g 3 V) INVENTOR. J74Ms Kile/Z5102 nQQQQ BY MMM/ flrrolemsx UnitedStates Patent 3,194,026 PGWER-REFREGERATHON SYSTEM James K. lLa Fleur,Hermosa Beach, Calif., assignor to The La Fleur Corporation, LosAngeles, Calif., a corporation of California Filed Get. 24, 1963, er.No. 318,564 37 Claims. (Cl. 62-88) The present application is acontinuation-in-part of my application Serial Number 87,311, filed Feb.6, 1961, for Method and Apparatus for Separation of Air and GaseousMixtures, and the disclosure of such prior application is incorporatedherein by reference thereto.

This invention relates to a new closed power-refrigeration system inwhich a gas is the common working medium in both a power cycle and arefrigeration cycle, that is, such cycles are interconnected so that thecommon working medium circulates between both cycles of the system.Alternatively, this invention may be viewed as a system comprised of aclosed gas turbine cycle having connected thereto a closed refrigerationcycle obtaining its motivation by bleeding a portion of the commonworking medium from and returning such medium to the power cycle.Further novel features of the present invention are the use of a commoncompressor for the power and refrigeration cycles; the use of a hotturbine in the power cycle and a cold turbine in the refrigerationcycle, with both such turbines feeding power to the common compressorthat provides compressed working medium gas to both cycles of thesystem; the use of a working medium having a critical point at or belowthe cryogenic temperature to be achieved by such refrigeration; and theattainment of cryogenic temperatures to the order of 2 Rankine with theemployment of a single expansion of the refrigerant working medium whichremains a gas thruout both cycles, and to effect such single expansionover a narrow, critical, pressure ratio that provides maxi mum cycleefiiciency.

The present invention has particular application to and involves theliquefaction of air and other gases such as helium and hydrogen, gaseshaving very low critical points; and has particular application in asystem for obtaining large heat transfers at cryogenic temperatures. Thepresent system is particularly suitable for economically liquefying manytons of air per day.

The basic elements of the system of the present invention are, in thefollowing order in the power cycle, starting with a compressor for agaseous working medium, the medium flows from the compressor to and thrua hot regenerator for imparting heat to the medium, thru a heater orfurnace for further heating the medium, thru a hot power turbine inwhich the medium expands, again thru the hot regenerator for removingheat from the medium, and then thru a heat sump to reduce the medium toambient temperature, and in the power cycle, suitable conduits to linksuch elements and suitable connecting means so that the hot turbinedelivers power to the compressor; and in the following order in therefrigeration cycle, starting with the above same compressor, from suchcompressor, bleeding some of the working medium from the power cycle toa heat sump to reduce the medium to ambient temperature, then to andthru a cold regenerator for removing heat from the medium, then to andthru a cold turbine for expansion of the medium and further temperaturereduction, to and thru a heat source, the refrigeration load, and thenback thru the cold regenerator to the compressor common to both powerand refrigeration cycles, and the refrigeration cycle having suitableconduits to connect such elements of the refrigeration cycle in suchorder and suitable connecting means so that the cold turbine deliverspower to the compressor.

"ice

The prior art processes and apparatuses for the liquefaction of air havebeen well review by Russell B. Scott in his book Cryogenic Engineeringpublished by D. Van Nostrand Company, Inc. Princeton, New Jersey, 1959.This book contains an extensive bibliography. According to presentusage, cryogenic engineering is concerned with temperatures below 240F., (Fahrenheit), or 220 R. (Rankine). Cryogenic gases may be consideredas those having critical temperatures below these temperatures.

The early Hampson air liquefier was a simple device in which air wascompressed to between 2000 and 3000 pounds per square inch (p.s.i.), itsstatic pressure, cooled to ambient temperature, purified, passed thru acounterflow heat exchanger, or regenerator, expanded into a chamber atatmospheric pressure to obtain the needed refrigeration by theJoule-Thomson effect, passed thru the heat exchanger to cool theincoming air, and then back to the compressor to be again compressed andrecycled until liquefaction occurred in the expansion chamber. The majordisadvantage of the Hampson process is the requirement for these highpressures and pressure ratios that entail heavy and expensivecompressing machinery.

Most of the advances in this field by Linde, Claude, and others havebeen to reduce the need for such pressures. This has been done by theuse of auxiliary or preliminary refrigeration systems to reduce thetemperature of the air before it enters the compressor and before itenters the counterfiow heat exchanger with the out flowing unliquefiedair components; and with the use of multistage expansion as in the Lindesystem; and with the use of cascades of liquefiers, each using adifferent refrigerant, as in the cascade air liquefier suggested byKeesom. The use of expansion engines instead of an expansion valve hascontributed to further efficiencies in the liquefaction of air. All ofsuch improved systems have added complexity to the simple process andsimple equipment of the original Hampson system. Thus, it is one of theobjects of the present invention to practice a cryogenic refrigerationprocess, and machinery therefor, having a large heat capacity and thathas the simplicity of a single expansion step with a small pressureratio as compared with the prior art.

The Hampson simplicity was partially recaptured in the Claude and Kapizacycles by the use of expansion engines instead of the Joule-Thomsoneffect. However, all of these systems were open, systems in which theworking medium, or refrigerant, was the gas, air, to be liquefied. Thisis a disadvantage in that contaminants move between the air and themachinery, and air is not the best refrigerant for its own liquefaction.

A closed refrigeration system for the liquefaction of gases has manyadvantages, such as freedom from atmospheric contamination and inarbitrary choice of static pressures and density of working medium, heattransfer characteristics, and boiling points, or critical temperatures.In a closed refrigeration system, one is not saddled with thecharacteristics of the gas to be liquefied in determining the workingmedium for the system, other than that the medium be capable ofachieving the desired refrigeration effect. I

The Phillips process of refrigeration, while a closed cycle using aregenerator and an expander, has been performed by the use ofreciprocating machinery. In that reciprocating machinery is not suitedfor large plants, the advantages of the Phillips process have never beenrealized in large scale gas liquefaction where it is desirable to employa system having a constant volume and a constant pressure ratio. Thus,it is a further object to operate the present process at constant volumeand under constant temperature and points of the cryogenic gases.

' is the low limit for Work in the cryogenic range.

ens gees of the Phillips system is found inzl-landbuch der Physik,

Kaltephysik I; Springer 1956,.and in United States patent to J. A. L.ljzer, 2,934,909, May 3, 1960. V I Specifically, it is an object of thepresent invention to devise ,a simple closed refrigerationcycleparticularly adapted for the liquefaction of 'air, and to use as aWork- 1ng medium in such system one of the gaseous elements having acritical point tempertaure below that. of the air components to beliquefied so that such may be carried out at or near atmosphericpressure. Thus, if oxygen and argon are to be liquefied, then nitrogenmay be used as the refrigerant working medium. If nitrogen is tdbeliquefied, then either neon, deuterium, hydrogen, or heli-' um, orcombinations thereof, would be used. Further,

in view of the use ofa refrigerant medium having a critical temperaturebelow that of the gases to be liquefied, it becomes possible to: operatethe refrigeration cycle so that the working mediunr is above itscondensation point thr'uout the cycle; and it is an object of thepresent ina vention to so operate. a refrigeration cycle.

Further, hydrogen and helium have the lowest boiling of using thesegases are heir greater heat content and their higher heattransfercoetficientsas compared with air. The .spec1fic heat ofhelium isabout'five'times and that of hydrogenabout thirteen'times that of air.Thus, with a closed cycle ,using either helium or hydrogen as the workmgfluid, substantial savings in equipment may be made a very considerablesaving in plant and opertaing costs.

' Having adopted the closed cycle using one of the gases spec1fied, andgottenaway from the limitations imposed by the use of the gas to beliquefied as the working medi Other desirable features choice basedpurely on economics However, in order to minimize the entropy gain inthe refrigeration side of .further diminishing the effect of the entropygain in the "expander turbine is to decrease the pressure ratio tothepoint where the-entropy gainof the'turbineis at least notdisproportionate as compared to the cold regenerator.

' This results ina rather low pressure ratio for the expander um, as setforth in the prior art, applicant is in a position to carry out hisprocess in the most efficient manner possible. Hence, it is anotherobject of the present invention to devise a simple closed cyclerefrigeration system for particularly well suited to moving largequantities of gas with low pressure differentials. Also the gas turbineis I a favorablesource of power in the range of the power needs for suchrefrigeration loads.

If the lowest temperature in a single expansion refrigera tion cycle isrequired to be reduced to lower and lowertemperatures, the effectivenessof the .cold regenerator must, of necessity, be raised to higher andhigher values in order 'to make the cycle work at all. For example, ifthe lowest temperaturerequiredis something in the order of zero degreesF., probably, no cold regenerator would be used. As the temperature islowered, the imperativeness of efiicient regeneration is increased. Asthe temperatures to be achieved in the present invention are at leastsomeelfectiveness be in the order of 99% for the system to reach and.effectively operate at 140 R.,' regardless of the other componentsefficiency. For the liquefaction of air, and using helium as therefrigerant, the cold regenerator 7 effectiveness would have to be above97% to obtain refrigeration load above losses. It methane were beingliquefied with nitrogen as'the refrigerant, the effectiveness of thecold regenerator could be as low as 95%, but this Within the acceptablelimits'of a cold regenerator effectiveness for a'given temperature,there is a reasonable freedom of what of the order of liquid nitrogenand less, colder, or Y less than 140. K, it is necessary that the coldregenerator tubine, as set forth herein. However, within the acceptablerange of low pressure ratios in the low temperature refrigeration areaforming the present subject matter, as the refrigeration temperaturetobe achieved is lowered toward absolute Zero, there is a small increasein pressure ratios for optimum performance. Regarding thesystem as awhole, including thehot side, the power side, it will be necessary,because. the cost of producing the cold in ,7 terms of inefficiencies isso much greater than producing shaft horsepower from the hot side of thesystem, to let the cold side control the design of the system. Thisbeing so, it will be necessary for the efi'iciency of the hotregenerator to' be higher than would normally be economically feasiblein apower generating gasturbine cycle. While the hot regeneratorefficiency may be lower than that for the cold regeneratorbecause theloss is easily made up by the supply of more heat to the power cycle,the pressure drop thruthe hot loop, the power cycle, must besubstantially that in the cold loop. These considerations set the hotregenerator efliciency above 90%, and preferably much higher.

In a refrigeration cycle that includes a. compressor I turbine,regenerator, an expander such as a turbine, and

a'liquefaction load, certain operating conditions therefor may beassumed such as the kind of gas tobe used in the system, the ambienttemperature for the compressed working gas entering the regenerat-or,the regenerator performance, the compressor efficiency, the after coolerv efficiency, and the expander effi'ciency. These assumptions are thoseinherent in the machines and d6VlCBS to be used and can beknown inadvance. Such assumptions include the desired temperature of the workinggas leaving the refrigeration load. With the ambient and refrigerantload outlet temperatures and the regenerat-or performance, the. expanderinlet and outlet temperatures may be -calculated. These values may beused to calculate the actual heat pumped from the load per unit ofworking medium. Also, these values may be used to calculate the curvesof the actual temperature-entropy diagram.

Further, by assuming various actual pressure ratios for therefrigeration cycle, with the other conditions constant, there may beobtained various indices of performance. These indicesmay beplottedagainst the various pressure ratios to give a performance curve thatwill indicate the optimum pressure ratio. Further, such performancecurves may be constructed for various working mediums such as nitrogen,neon, helium and hydrogen, at various refrigerate temperatures.Applicant has found that for all ofthese gases as working mediums thereis alimitation defining an optimum pressure ratio range for a cycle or asystem for satisfactory performance. Inherent in this satisfactoryperformance from an engineering and cost point of view is therequirement of high regenerative efficiency and high expander efficiencyas well as high efficiencies in the other heat transfers in the cycle.This defining limitation for optimum pressure ratio range forsatisfactory performance, includes those required minimum apparatusefficiencies. The values of these apparatus efficiencies has beenpreviously discussed.

The optimum pressure ratio is that ratio having the highest, the maximum(M), index of performance, the peak of the performance curve. Applicanthas found that using nitrogen or, but in particular, neon, deuterium,hydrogen, or helium, as a gas, or combinations of such gases, for theworking medium, the refrigerant, that the range of performance indicesvariation, that is the limits of pressure ratio variation, are: (a) thelow pressure ratio limit is (the optimum pressure ratio value plus one)divided by (two); and (b) the high pressure ratio limit is (twicethe-optimum pressure ratio value less one). This may be symbolized bydesignating the optimum pressure value as N, then the limits are:(M+l)/2 and 2M1. The use of ratios outside of this range make ituneconomical or impossible to vaccomplish useful work by means of themechanisms and processes of the present invention in the temperaturerange required for the liquefaction of air and its components, and suchrefrigerant; by a single expansion step of the refrigerant and for suchliquefaction at substantially atmospheric pressure. For the liquefactionof helium by the use of helium as the refrigerant, the helium to beliquefied must be held above the cycle pressure but the neededrefrigerative effect can be achieved by a single expansion of therefrigerant. The limits of pressure ratio variation set forth above areindependent of the absolute pressure at which a cycle or systemoperates.

As the outlet temperature of the working medium from the refrigerationload is lowered, the temperature drop across the load, and the expander,is decreased, and such decreases are exponential functions of theexpander inlet temperature. This means that as absolute zero isapproached, the pressure and temperature ratios, expander inlet tooutlet, become small as set forth above and as compared to priorpractices. To obtain an expander outlet temperature of 128 R. and anoutlet temperature of 139 R. on the load outlet system, an optimumpressure ratio of about 1.5 must be achieved, using helium, by means ofthe present invention. If gaseous helium is used to liquefy hydrogen,the temperature ratio needed is still obtainable as their boiling pointsdiffer by 29,

and the present process will operate at a much smaller temperature ratioat such temperatures. A pressure ratio of substantially 2.4 would besufficient, with the same plant efiiciency. Certainly, with the presentprocess and reasonable efiiciencies, the optimum pressure ratio withhelium for the liquefaction of hydrogen, should be less than 2.5.Thruout the cryogenic range from 220 R. to 2 R., the optimum pressureratio should be between 1.25 and 3.0, that is with reasonableefficiencies in plant operation and according to the present inventionusing helium, hydrogen, deuterium, or neon as the working medium inturbine machinery. If nitrogen were to be used as a refrigerant down to220, the optimum pressure ratio would increase to 2.425. it is an objectof the present invention to device a plant and process therefor in whichrefrigeration is obtainable in such cryogenic range with such pressureratios using such gases in turbine machinery.

If the value of the pressure ratio is greatly increased above the designpressure range, the relative increase in expansion turbine lossesreduces the cycle performance and if the ratio is slightly decreasedbelow the range, the losses associated with the cold regenerator becomelarge relative to the temperature drop in the expansion turbine, againreducing cycle performance. Applicant has found that outside of theabove described range such losses become unbearable in the face of goodpractice within the present invention. Thus it is an object of thepresent invention to construct and operate a closed cycle constantvolume system for cryogenic refrigeration using such refrigerant workinggases and pressure ratio ranges.

In summary, an object of the present invention is the construction ofmachinery for and the performance of a process for obtaining cryogenicrefrigeration temperatures by means of a closed system operating atconstant volume, at constant low temperature and in such low pressureexpansion ratio ranges, and at low static pressure. Further, it is anobject to operate such a system with a single expander or expansionstep. Specifically, it is an object of the present invention to operatesuch a closed system at pressure ratios between 1.15 and 3.85. Anotherspecific object of the invention is to devise such machinery and processof operation at static pressures less than five hundred pounds persquare inch. A further specific object is to operate such a system forthe liquefaction of air components, and to use in the system helium,hydrogen, deuterium, or neon as the refrigerant working medium, and,particularly to use either helium or hydrogen, those elements havingonly K-shell electrons, as they have the best specific heat coefficientsand the lowest critical temperatures. Yet another specific object is tocarry out such air liquefaction and separation at atmospheric pressure.

The adoption in a refrigeration cycle of the above described pressureratio range for the expansion turbine sets the expansion ratio for acompressor turbine in such cycle. Also, if the compressor is powered bya gas turbine and if all three, gas turbine, compressor, and expander,use the same working gas in a single closed system, the expansion ratioof the power turbine is the same as that of the compressor and theexpander, excepting small differences due to differences in theparasitic losses of the two cycles, the power cycle and therefrigeration cycle. Further, as previously explained, the coldregenerator ethciencies found to be required, require the regenerator inthe power cycle to have high efiicicncy. This uniformity of pressureratios and regenerator cfficiencies thruout a power-refrigeration systemis another object of the present invention. Thus it is another object ofthe invention to operate a gas turbine as a power source for therefrigeration load, and to do so at such optimum pressure ratios.Further, such paralleling of optimum operating conditions means that thetwo systems, power and refrigeration, can be combined into a singlesystem using a working medium in common and a common compressor, with apower turbine, an expansion turbine, and a compressor turbine allmounted on a common shaft for the interchange of power between theturbines. Thus, it is another object of the invention to devise arefrigeration-power system in which is circulated a common gas Workingmedium, and, further, that there be a direct exchange of power in suchsystem.

The above mentioned defects of the prior art devices are remedied andthe aforementioned objects achieved by the use of suitable equipmenthaving, briefly, in operation therein closed gas turbine andrefrigeration cycles operating with a common compressor turbine directlyconnected to a power turbine and a refrigeration expansion turbine, andwith a common working gas medium, and operating such cycles at constantvolume and with the pressure ratios described.

A system such as described briefly above is schemati cally illustratedin the accompanying drawin".

For the purpose of the following description and by Way of example, thesystem will be described as using helium as the working gas medium forboth the power and refrigeration cycles. The temperatures and pressureshereinafter are by way of example, and are variable within the abovementioned limits. All pressures are pounds per square inch absolute(p.s.i.) and tempera- 7 V ,7 V tures are degrees Rankine R;).'Assumingthe whole system of power and refrigeration has been inoperation for a suificient time to reach the intended operatingconditions of temperature and pressure, helium enters a compressorturbine lb at a pressure of 181 psi. and an ambient temperature of 530.Helium is discharged from the high pressure side of the'compressor at268 p.s.i. and 618. The flow from the compressor outlet conduit 11 isdivided into two high pressure side streams, namely a power stream whichflows thru one branch 12, or power loop, and a refrigeration streamwhich flows thru 'another branch 113,02 refrigeration loop, of theoutlet conduit 11. The high side ofthe power stream, or hot stream,first passes thru one side ofa regenerator' 14,

the power or hotregenerator, where it is heated to 1493 From ther'egenerator the high side power stream passes thru a combustion chamberheat exchangercoil 15 which serves to heat the gas to 1660". Anysuitable fuel or source ofheat, as the coil 16, maybe used. The powerstream is led to and used to driv'e a hot turbine 17 which provides alarge part of the power for the compressor 1d. Thegas expands and coolsin the turbine, the, pressure 14 98", and thenpassesthru the other side,the low pressure side, of the hot regenerator 14 where it is cooledwhile heating the high side power stream in counter cur rent fiowthereto, to'approximately the compressor dissnaapae g means, or byelectrical or'magn'etic means. Particularly, the starting motor may beclutched to the shaft by a clutch 36 so that when its work of startingthe system is over it may be disconnected'therefrom. Also, the cold-nish electrical power by means of the generator 22 for turbine 21 maybe directly coupled to the compressor 10 by a clutch 37. Thus, the coldturbine may deliver power directly by shaft means to the compressor orit may furany desired use.

By the above described process and equipment, applicant has evisedsimple means for the economical con- .densationj and liquefaction of theso-called cryogenic, or

' working medium is intermingled for both systems by the use of a commoncompressor 1%. The defects of the prior art inherent in the use of opencycles is remedied dropping to 190 p.s.i. andthe temperature dropping toi charge temperature. While, generically, this iscalled regeneration ofthe gas, or working medium, applicant uses the terms, generation anddegeneration to indicate the gain or loss of heat, respectively, in aregenerator. Finally the gas passes thru a precooler 18 from which it isreturned to the compressor 10. The precooler may be water or air cooled,and serves as a heat sump for the duit 13', passes first thru a heatsump 19, or after-cooler, where it is cooled to 530, the ambienttemperature, the

pressure drop being slight, about 5 psi. The stream then passes thru aregenerator 2b, the cold regenerator, where 7 it is cooled, ordegenerated, to 141. The gas emerging from the regenerator drives aturbine ZLcalled the cold turbine, wherein the gas expands with'a dropin temperature to 128. The cold turbine 21 servesas a source of power toa generator 22 connected thereto by a shaft'ZS.

The cooled low pressure stream of helium then passes,

thru heat exchanger coil 24 or other conduit means or high heatconductivity which'acts as the refrigeration. load for the system andthe cycle. From the load coil 24, the

low pressure helium returns to the cold regenerator as where it servesto cool the high side helium. The helium then completes its.refrigeration loop by returning to the compressor at ambient temperatureand compressor inlet pressure of 181 p.s.i. The material giving heat tothe refrigerationload is passed thru a coil 26 in heat exchangerelationship with the refrigerant coil 24, the coils 24, 26 constitutinga heat exchanger. Thismaterial to be cooled may be a gas such as air tobe liquefied and its components separated as by rectification. Suchrefrigerate gas is moved counter current to the flow of the heliumrefrigerant. This is an important aspect of the use of a closed cycle,that for the liquefaction and separation of gas components the flow ofrefrigerant and refrigerate may be in counter current heatexchange'relationsl'iip.v i

' 7 Initially, in placing the system in operation, a starting electricmotor 34. or other external source of motive bines until the systemreaches a point Where it is thereby .the use of a closed system, orcycles, for both power and refrigeration.

This allows the use of the one gas medium best suited to a particularproblem, both power and refrigeration,-the best as to specific heatcharacteristic and the best as to critical temperature. Also, theselectivity of working medium, allows the refrigeration and thepower,each to be had by a single expansion step, by the use of the singleexpansion cold'turbine 21 and the hot turbine 17.

The system is started in operation by first supplying cooling water orair to the heat sumps 13, 19, by supplying gas or air to be condensed tothe refrigerate coil 26, and then by spinning the compressor 10 andturbines 17, 21 by means of the motor 34 to start the gas working mediumcirculating in both loops 12, 13 of the cycles and the system, Once theturbines are up to speed, heat is supplied to the furnace, or heat inputexchanger 15, so that the hot turbine 17, will take on the compressorswork of circulating the working medium, and power to the starting motor34 may be discontinued and the motor disconnected from the turbinescommon shaft 35. When the refrigeration coils 24, 26 are reduced intemperature to the proper degree, air components will be liquefied bypassage thru the coil 26.

. Ifhelium, hydrogen, or neon, or a combination thereof, is used as theworking medium, such of the permanent present system.

The system will be operatedon the temperature and a pressuredifferentials of working medium previously described, once it hasreached equilibrium. These differentials, or operating conditions, arethose that will allow the system, to operate with a minimum of powerinput. Further, these operating conditions are new in the closed cyclepower and refrigeration field, and in the operation afterself-sustaining. "All of thet'urbines 10, 17, 21. and

the starting motor may be mounted on a single shaft 35 or-they may becoupled by mechanical or hydraulic of turbines. The fact that changes inthe refrigeration load directly effect a change in the power productionsystem, by the use of acommon working medium, and are therebycompensated'for by changes in density of such medium resulting fromchanges in the load, is an importantfactor in system stability. p

I No'disclosure is made herein of the special relationships of thepresently disclosed invention to the problems of and processes of gasliquefaction and separation,

other than those found in connection with the discussion of thepriorart, andthe statement that air may be-liquetied in therefrigerateload coil 26 at atmospheric pressure when helium, hydrogen,or neon is used as the refrigerant.

Having thus described my invention, the operation of its process andmachinery for the performance of such 9 process, the products obtainabletherefrom, and a specific example of the temperatures and pressuresusable within the defined critical range, I claim:

1. A closed cycle power-refrigeration process in which a cryogenic gasis the working medium in both a power cycle and a refrigeration cycle ofa system, comprising: establishing a closed system and, in said system,effecting a power cycle by circulating and acting on said gas thru thefollowing seriatum steps, compression, generation in a firstregenerator, heating, expansion to accomplish work, degeneration in suchregenerator, cooling, and again compressing to complete such powercycle, and in which power cycle such work is used for such compression;and, in such system, effecting a refrigeration cycle by circulating andacting on said gas thru the following seriatum steps, bleeding gas fromsaid power cycle immediately after said compression, coolingdegenerating in a second regenerator, expanding to reduce thetemperature of said gas, adding heat from a refrigeration load,generating in such second regenerator, and returning such bled gas tosaidpower cycle for compression.

2. The process of claim 1 in which the expanding of said gas in saidrefrigeration cycle is accompanied'byth'e derivation of power from suchexpansion, and in which process such power is used for the compressionof said gas.

3. The process of claim 1 in which the pressure ratio in such system isheld between the following pressure ratio limits: the low limit is (theoptimum pressure ratio value plus one) divided by (two) and the highpressure ratio limit is (twice the optimum pressure ratio value) less(one).

4. The combination of claim 3 in which said optimum pressure ratio isbetween 1.25 and 3.0.

5. The combination of claim 1 in which each of said regenerators has aneffectiveness better than 90%.

6. The combination of claim 1 in which said second regenerator has aneifevtiveness better than 95%.

7. The combination of claim 1 in which said first regenerator has aneffectiveness better than 90%, and said second regenerator has aneffectiveness better than 95%.

8. The process of claim 1 in which said gas in said cycles remains a gasduring the whole of said cycles.

9. The combination of claim 8 in which said gas is helium, hydrogen,deuterium, or neon.

it). The combination of claim 1 in which said compression, expansion toaccomplish work, and expansion to reduce temperature, each has apressure ratio held between the following pressure ratio limits: the lowlimit is half the sum of (the optimum pressure ratio value plus one)divided by (two) and the high pressure ratio limit is (twice the optimumpressure ratio value) less (one).

1. The combination of claim 19 in which said gas is helium, hydrogen,deuterium, or neon.

12. The combination of claim 1 in which the temperature achieved by saidexpansion is less than 220 R.

13. The combination of claim 11 in which the temuerature achieved bysaid expansion is less than 140 R.

14. In a method of providing very low temperature refrigerationutilizing a very low boiling point gaseous refrigerant medium in aclosed system that comprises the steps of confining the medium atambient temperature at a pressure of several atmospheres, compressingsaid medium substantially, and dividing the compressed medium into afirst stream and a second stream; heating the first stream to raise thetemperature thereof substantially, allowing the heated first stream toexpand and deriving power from such expansion, and returning suchexpanded first stream to such compression step; and cooling the secondstream, allowing the second stream to expand and deriving power fromsuch expansion, allowing the expanded second stream to absorb heat at avery low emperature, and utilizing the resulting heated second streamfor said aforementioned cooling of the second it stream to provide afurther heated second stream, and returning such further heated secondstream to such compression step.

15. In a closed cycle very low temperature refrigeration system adaptedto contain a very low boiling point gas under pressure as therefrigerant medium, a compressor having an exhaust side and an intakeside, a first turbine mechanically connected to drive said compressor, asecond turbine mechanically connected to drive said compressor, conduitmeans extending from the exhaust 'side to the intake side of thecompressor providing a hot circuit for flow of a part of the mediumleaving the compressor, conduit means extending from the exhaust side tothe intake side of the compressor providing a cold circuit for the flowofthe remainder of the medium leaving the compressor, said first turbinebeing connected into said hot circuit and said second turbine beingconnected into said cold circuit, means for supplying heat to the mediumin said hot circuit at a region between the compressor exhaust side andsaid first turbine, means between said compressor exhaust side and saidsecond turbine in said cold circuit for cooling the medium therein, anda load heat exchange means between said second turbine and thecompressor intake side in said cold circuit for extracting heat from aload.

16. A refrigeration system as set forth in claim 15 in which the meansbetween the compressor and the second turbine in the cold circuit forcooling the medium includes a regenerator heat exchanger through whichthe medium flows before reaching said second turbine and after leavingthe load heat exchange means.

17. A power-refrigeration process in which a gas is the Working mediumin both a closed power cycle and a closed refrigeration cycle, suchcycles forming a closed system for the practice of such process,comprising: establishing a closed system wherein there is circulated agas and, in said system, effecting a power cycle by circulating andacting on said gas by means of the following seriatum steps,compression, a first generation heat transfer, heating, expansion withthe accomplishment of work, degeneration to said first generation heattransfer, cooling to ambient temperature, and again compressing tocomplete such power cycle, and in such power cycle using such power forsuch compression; and in such system, eifecting a refrigeration cycle bycirculating and acting on said gas by means of the following seriatumsteps, bleeding gas from said power cycle immediately after saidcompression, cooling to ambient temperature, a second degeneration heattransfer, expanding with the ac complishment of temperature reduction,adding heat from a refrigeration load, generation to said seconddegeneration heat transfer, and returning such bleed gas to said powercycle for compression.

18. The process of claim 17 in which said gas in said system remains agas at all time. I

19. The process of claim 17 in which the expanding of gas in saidrefrigeration cycle is accompanied by the production of work that isused for the compression of said gas.

20. The process of claim 18 in which said gas is helium, hydrogen, orneon.

21. The process of claim 17 in which said refrigeration cycle, theexpansion of said gas is accomplished with the production of both workand said temperature reduction.

22. The process of claim 18 in which said gas is a gas having a criticaltemperature equal to or lower than the critical temperature of nitrogen.

23. The combination of claim 18 in which said gas is from the grouphaving only K-shell electrons.

, 24. A power system having closed but interconnected hot and cold loopsfor the conduct of a gas working medium in such loops, a compressorhaving an inlet and an outlet, said compressor being common to suchloops and each loop having a connection to the inlet and the outletthereof to provide such loops" interconnection,

said hot loop having therein, in addition to said compressor, in :seriesfrom said compressor outlet to said "compressor inlet: a hotregenerator, a high temperature heat source, the inlet of a hot turbine,such hot turbine,

the outlet of such turbine, said hot reg'enerator, and a hot loop heatsump; said cold loop having therein, in

addition to said compressor, in series from said compressor outlet tosaid compressor inlet; a cold loop heat sump, a cold regenerator, theinlet of a cold turbine, such cold turbine, the outlet of such-coldturbine, alow temperature heat source, and said cold regenerator; bothof said turbines being operated forthe production of power,

and said compressor of power. 7 I

25. A power system having closed but interconnected being operated forthe consumption first and second loops for the conduct'therein of a gasworking medium, a compressor interconnectingv said loops, a separateturbine connected in each of said loops and dividing it into a highpressure side and a low pressure side, each loop having its highpressure side and its low pressure side arranged in regenerativerelationship, and

a regenerator in eachloop providing such relationship; the first of saidloops having a high temperature heat source in its high pressure' side'between its regenerator and turbine, and a heat sump in its low pressureside thru said hot loop sump to said compressor; saidcold loop havingtherein, in addition to said compressor, in

series from said compressor outlet to said compressor inlet: a cold loopheat sump," a cold regenerator, the inlet of a cold turbine, such coldturbine, the outlet of such cold turbine, a: low temperature heatsource, and

said cold rcgenerator, the temperature ofsaid gas from said compressorin said cold loop being seriatum progressivel-y decreased in'saidcoldloop sump, cold regenerator,

,, interconnected hot and cold loops for the conduct of a between'itsregenerator and the. compressor; and the a second of said loops having alow pressure temperature heat source in its low side between itsregenerator and turbine, and a'heat sump in its highpressure sidebetween its regenerat or and the compressor; both of said turbines beingoperated for the production of power, and said compressor'being operatedfor the consumption of power.

26. The combination of claim in which the working medium isja gas havinga critical temperature equal to or lower than that of nitrogen. V

27. In a method of providing very low temperature refrigerationutilizing a very low boiling point gaseous refrigerant medium in aclosed cycle which comprises the steps of confining the medium atambient temperature at a pressure of several atmospheres, compressingsaid medium substantially,. dividing after compression and before othersteps the compressed medium into a first stream and a second stream,heating; the first stream to raise the temperature thereof.substantially, allowing the heated first stream to expand and derivingmechanical energy therefrom toprovide part of the power required 'tocompress the medium, cooling the second stream, al-

lowing the second stream to expand and deriving mechanical energytherefromlto provide theremainder of the power required tocompress themedium, allowing the expanded second stream to absorb heat at a very lowtemperature, and utilizing the resulting heated second stream for-saidaforementioned cooling o'fthe second stream for reterconnected hot andcold loops for-the conduct of a gas working medium thru such loops, acompressor having an inlet andan outlet, said compressor being common tosuch loops and each loop having a connection to the inlet and theoutlet'thereof to provide such loops interconnection, said-hot loophaving therein, in addition to said compresson'in series from saidcompressor outlet to said compressor inletza hot regenerator, a heater.having a high temperature 'heat source, the inlet of a hot turbine,such hot turbine, theoutlet of such turbine,

said hot regenerator, and a hot loop heat sump, the

temperature of said gas from, said compressor in said gas working mediumthru such loops, a compressor having an inlet and an outlet, saidcompressor being common to such loops and each loop having a connectionto the 'inlet and the outlet thereof to provide such loopsinterconnection, said hot loop having therein, in addition to .saidcompressor, in series from said compressor outlet to said compressorinlet: a hot "regenerator, a heater having a high temperature heatsource, the inlet of a hot turbine, such hot turbine, the, outlet ofsuch turbine, said hot regenerator, and a hot loop heat sump, thetemperature of said gas from said compressor in said hot loop beingseriatum progressively 'increased in said hot regenerator and saidheater, and then progressively decreased in saidhot turbine, said hotregenerator, and thru said hot loop sump to said compressor; said cold'loophaving therein, in addition to said compressor, in

sively decreased in said cold loop sump,,cold regenerator,

and cold turbine, and then progressively increased through saidheatisource andsaidcold regenerator to'said compressor. I t a 32. Apower-refrigeration system in which a gas is the Working medium in botha closed power cycle and a closed refrigeration cycle,said cycles beingcombined in a unitary system, which comprises circulating said gas in apower cycle and including therein the steps of compassage thereofthrough a first prime mover, passing said hot expanded gas in heatexchange relation with said initially compressed gas to reduce thetemperature of said expanded gas, and again compressing said gas tocomplete i said power cycle; circulating said gas in a refrigeration,Cycle and including the'stcps of taking a portion of said compressedgas from said power cycle, cooling said compressed gas portion, passingsaid cooled compressed gas in heat exchange relation with a coldexpanded gas and further'lowering the temperature of said cooledcompressedgas, expanding the exiting cold compressed gas 1 by passagethereof through a second prime mover, passing I change relation withsaid cooled compressed gas to add hot loop being seriatumprogressivelyincreased in'said 7 hot regenerator and said heater, and thenprogressively decreased said hot turbine, said 'hotregeneraton'and heatto said gas leaving said refrigeration load, and returning saidlast'rnenticned gas to said power cycle for compression. a i

33. The process of claim 32, wherein the power resulting from theexpansion of said hot compressed gas in said first prime mover isemployed for the compression of said gas.

34. The process of claim 32, wherein the power resulting from theexpansion of said hot compressed gas in said first prime mover and fromthe expansion of said cold compressed gas in said second prime mover areemployed for the compression of said gas.

35. The process of claim 34, wherein said gas is helium and wherein thepressure ratio of said system is maintained such that the low pressureratio limit is (the optimum pressure ratio value plus one) divided bytwo, and the high pressure ratio limit is (twice the optimum pressureratio value) less one.

36. The process of claim 32, in which the pressure ratio of said systemis maintained such that the low pressure ratio limit is (the optimumpressure ratio value plus one) divided by two, and the high pressureratio limit is (twice the optimum pressure ratio value) less one.

37. The process of claim 36, wherein the pressure ratio in said systemis between 1.15 and 3.85.

References Cited by the Examiner UNITED STATES PATENTS 1,264,807 4/ 18Jeiferies 6288 1,440,000 12/22 Bonine 62402 2,929,217 3/60 Collman 625915 ROBERT A. OLEARY, Primary Examiner.

1. A CLOSED CYCLE POWER-REFRIGERATION PROCESS IN WHICH A CRYOGENIC GASIS THE WORKING MEDIUM IN BOTH A POWER CYCLE AND A REFRIGERATION CYCLE OFA SYSTEM, COMPRISING: ESTABLISHING A CLOSED SYSTEM AND, IN SAID SYSTEM,EFFECTING A POWER CYCLE BY CIRCULATING AND ACTING ON SAID GAS THRU THEFOLLOWING SERIATUM STEPS, COMPRESSION, GENERATION IN A FIRSTREGENERATOR, HEATING, EXPANSION TO ACCOMPLISH WORK, DEGENERATION IN SUCHREGENERATOR, COOLING, AND AGAIN COMPRESSING TO COMPLETE SUCH POWERCYCLE, AND IN WHICH POWER CYCLE SUCH WORK IS USED FOR SUCH COMPRESSION;AND, IN SUCH SYSTEM, EFFECTING A REFRIGERATION CYCLE BY CIRCULATING ANDACTING ON SAID GAS THRU THE FOLLOWING SERIATUM STEPS, BLEEDING GAS FROMSAID POWER CYCLE IMMEDIATELY AFTER SAID COMPRESSION, COOLING,DEGENERATING IN A SECOND REGENERATOR, EXPANDING TO REDUCE THETEMPERATURE OF SAID GAS, ADDING HEAT FROM A REFRIGERATION LOAD,GENERATING IN SUCH SECOND REGENERATOR, AND RETURNING SUCH BLED GAS TOSAID POWER CYCLE FOR COMPRESSION.